Provide fake endoint in tests

With grpc/grpc-go#5732 the grpc library
validates the presence of the endpoint information:
> client: return an error from Dial if an empty target is passed and no custom
> dialer is present; the ClientConn would otherwise be unable to connect and perform RPCs

src/autoscaler/metricsforwarder/server/server_suite_test.go

@@ -58,6 +58,7 @@ var _ = SynchronizedBeforeSuite(func() []byte {
 			CertFile:   filepath.Join(testCertDir, "metron.crt"),
 			CACertFile: filepath.Join(testCertDir, "loggregator-ca.crt"),
 		},
+		MetronAddress: "invalid-host-name-blah:12345",
 	}
 	serverConfig := config.ServerConfig{
 		Port: 2222 + GinkgoParallelProcess(),